1. Field of the Invention
The present invention relates to a crank assembly for drivingly interconnecting a plurality of connecting rods to a common crank pin of a crankshaft.
2. Prior Art
Reciprotacting piston machines of the type employing a radial array of cylinders with pistons movable in the cylinders are well known. By way of example, radial engines of this type have had extensive use in propellor driven aircraft.
In machines of this type, one proposed construction calls for a plurality of connecting rods to be coupled directly to a common crank pin. Where this approach is taken, it is common to provide one of the commonly coupled connecting rods with a bifurcated end which journals the crank pin at two axially spaced locations, and to journal the remainder of the commonly coupled connecting rods on the crank pin at locations between the bifurcations in an effort to balance the forces which are applied to the crank pin. Ordinarily, however, it has not been feasible to connect more than two connecting rods to a common crank pin.
Another proposal utilized in radial engines has been to designate one of the connecting rods as a master connecting rod, and to articulate other connecting rods on the master rod. The master rod is used for timing control, and the auxiliary rods transmit power to the master rod. Since the auxiliary rods are not connected directly to a crank pin but rather to the master rod at various individual points along the length of the master rod, the movement rates of the master rod and of the auxiliary rods do not always conform and thereby give rise to difficulties in balancing the system for smooth, optimum operation.
A problem common to both of these proposals has been that of design freedom being limited with regard to such factors as the number of pistons that can be employed, the stroke length, and connecting rod lengths and configurations. Moreover, each of these proposals calls for the use of a number of differently configured, specially formed connecting rods. Still another drawback has been an inherent lack of symmetry of the system components, and this has required the use of compensating measures such as adjustments in timing gears and in the positioning of camshaft cams for actuating inlet and exhaust valves.
These and other drawbacks may explain the reluctance to employ radial piston engines for wider fields of application, for example, to power land driven vehicles, particularly motorcycles. Radial engines are much quieter in operation than are other types of internal combustion engines and would therefore be especially advantageous for use on motorcycles to replace the extremely noisy engines commonly used on these vehicles.